In recent years, rotary electric machines have been designed for higher output, which has been demanding an increase of power density. The increase of power density, however, has been leading to an increase in heat density, making elevated temperatures of coils and permanent magnets a problem. Since permanent magnets, in particular, may suffer demagnetization at high temperatures, it is desirable to increase cooling efficiency.
PTL 1 discloses an arrangement that provides a path of a cooling medium at the outer periphery of a stator core of a rotary electric machine. A cooling medium, which changes from the liquid phase to the gas phase, is allowed to flow in the path, so that the cooling medium absorbs heat generated at the stator coils.
PTL 2 discloses a rotary electric machine having a rotor cooling arrangement as described below. A hole is provided in a rotor shaft. An inside air fan, which allows the inside air to pass through the air hole and through a gap between a stator and a rotor, and an outside air fan, which allows the outside air through, are provided. In addition, a heat exchanger for performing heat exchanging between the inside air and the outside air is provided at the outside of the stator.